Conventional vibratory apparatus for controllably vibrating a feed bowl typically includes a driver power unit which delivers a sequence of impulses to a drive coil or solenoid. The conventional driver power unit typically includes a rheostat which manually controls a magnitude of the impulses delivered to the drive coil to controllably vibrate the feed bowl. The feed bowl typically contains objects which are to be fed- to a work station via a chute.
As the objects exit the feed bowl via the chute, the feed bowl load becomes lighter while the magnitude of the impulses controlled by the rheostat remains the same. As a result, the feed bowl may vibrate at a higher amplitude which increases a feed rate of the feed bowl. An operator must continually adjust the rheostat to obtain a desired constant amplitude of vibration to provide a constant feed rate. Much time and expense would be saved by increasing the capability of an already installed conventional driver power unit through a retro-fit attachment which would provide automatic maintenance of the desired constant vibration amplitude.
Conventional automatic vibratory controllers frequently have a drawback when used with feed bowls designed to mechanically resonate at a frequency selected for maximum efficiency. On starting up, the feed rate undershoots and overshoots a desired steady-state feed rate as capacitive elements of the controller reach steady-state voltages.